Molded plastic package with heat sink and enhanced electrical performance

Abstract

A molded plastic package for semiconductor devices incorporating a heat sink, controlled impedance leads and separate power and ground rings is described. The lead frame of the package, separated by a dielectric layer, is attached to a metal heat sink. It has more than one ring for power and ground connections. The die itself is attached directly onto the heat sink through a window on the dielectric and provides high power dissipation. The package is molded using conventional materials and equipment.

What is claimed is:  
     
       1. A plastic molded package, comprising: 
       a heat sink having an upper surface and a lower surface;  
       a ceramic ring attached to said lower surface of said heat sink, said ceramic ring having an aperture exposing a portion of said lower surface of said heat sink;  
       a semiconductor die attached to said exposed portion of said lower surface of said heat sink using a thermally conductive adhesive;  
       a lead frame having a plurality of leads extending outside of said plastic molded package, said lead frame being attached to said ceramic ring, said lead frame being formed integrally with a downset interposer ring which is attached to said lead frame by a plurality severable tie bars; and  
       an encapsulation enclosing said ceramic ring, said lead frame other than said portion of said leads outside of said plastic molded package, and said semiconductor die.  
     
     
       2. A plastic molded package as in claim  1 , wherein said ceramic ring is attached to said heat sink by an adhesive film. 
     
     
       3. A plastic package as in claim  1 , wherein said ceramic ring comprises material selected from the group consisting ceramic materials, epoxy materials and a dielectric sheet material. 
     
     
       4. A plastic package as in claim  1 , wherein said heat sink comprises a material selected from the group consisting of oxygen free high conductivity copper, copper/molybdenum/copper laminate, copper/tungsten/copper laminate and beryllium composites. 
     
     
       5. A plastic package as in claim  1 , wherein said exposed portion of said heat sink is plated with a film of nickel. 
     
     
       6. A plastic molded package, comprising: 
       a heat sink having a base portion and a raised portion protruding above said base portion, said base portion having a lower surface and said raised portion having an upper surface, said lower surface having a larger surface area than said upper surface;  
       a dielectric ring attached to said lower surface of said heat sink, said dielectric ring having an aperture exposing a portion of said lower surface of said heat sink;  
       a semiconductor die attached to said exposed portion of said lower surface of said heat sink using a thermally conductive adhesive;  
       a lead frame having a plurality of leads extending outside of said plastic molded package, said lead frame being formed integrally with a downset interposer ring which is attached to said lead frame by a plurality of severable tie bars; and  
       an encapsulation exposing said upper surface of said heat sink to the ambient and enclosing said base portion of said heat sink, said dielectric ring, said lead frame other than said portion of said leads outside of said plastic molded package, and said semiconductor die.  
     
     
       7. A plastic molded package as in claim  6 , wherein said surface of said raised portion is free of corners. 
     
     
       8. A plastic molded package as in claim  6 , wherein said surface of said raised portion is circular. 
     
     
       9. A plastic molded package as in claim  6 , wherein said base portion further comprises a plurality of conical protrusions enclosed in said encapsulation. 
     
     
       10. A plastic molded package as in claim  6 , wherein said base portion of said heat sink have a plurality of through holes filled by said encapsulation. 
     
     
       11. A plastic molded package as in claim  6 , wherein said dielectric ring is thermally conductive, and wherein said dielectric ring is attached to said lead frame. 
     
     
       12. A plastic package as in claim  6 , wherein said dielectric ring a material selected from the group consisting of ceramic materials, epoxy materials, and a dielectric sheet material. 
     
     
       13. A plastic molded package, comprising: 
       a heat sink having an upper surface and a lower surface;  
       a dielectric ring attached to said lower surface of said heat sink, said dielectric ring having an aperture exposing a portion of said lower surface of said heat sink;  
       a semiconductor die attached to said exposed portion of said lower surface of said heat sink using a thermally conductive adhesive;  
       a lead frame, attached to said heat sink, having (i) a plurality of leads extending outside of said plastic molded package, and (ii) a one-piece interposer ring downset towards said semiconductor die relative to said plurality of leads, said interposer ring being formed integrally with said leads of said lead frame and being attached to the remainder of said lead frame by a plurality of severable tie bars; and  
       an encapsulation enclosing said dielectric ring, said lead frame other than said portion of said leads outside of said plastic molded package, and said semiconductor die.  
     
     
       14. A plastic package as in claim  13 , wherein said one-piece interposer ring is severed into a plurality of electrically isolated sections. 
     
     
       15. A plastic package as in claim  14 , wherein each of said electrically isolated section is supported in said encapsulation by tie bars of said lead frame. 
     
     
       16. A plastic package as in claim  14 , wherein one or more of said electrically isolated sections of said interposer ring is electrically shorted to said heat sink. 
     
     
       17. A plastic package as in claim  16 , wherein said one or electrically isolated sections are shorted to said heat sink by a layer of electrically conductive adhesive. 
     
     
       18. A plastic package as in claim  14 , wherein said electrically isolated sections of said interposer ring are electrically shorted to one or more leads of said lead frame. 
     
     
       19. A plastic molded package as in claim  13 , wherein said dielectric ring is thermally conductive, and wherein said dielectric ring is attached to said lead frame.